Power amplifiers are typically used to amplify a signal prior to transmission over a network, such as, for example, a cable network or a wireless network, and power management is an issue of growing concern as systems increase in complexity while decreasing in size. This is especially true for battery operated systems. Additionally, some types of network receivers and/or protocols impose requirements on received power levels at the receiver regardless of the distance from the transmitter. Transmitters may therefore need to adjust their output levels using, for example, a programmable gain amplifier that is continuously adjustable over a range of amplitudes. Furthermore, some types of transmission are intermittent, for example, time multiplexed transmission.
There exists a class of transmitters that use amplifiers which employ a transconductance stage (a voltage controlled current source) coupled to an output stage. The output stage typically requires a voltage supply for the output stage that requires a DC offset to prevent saturation of the transconductance stage. The output stage, therefore, consumes power at a relatively high rate that is related to the maximum signal amplitude that may be transmitted rather than the instantaneous signal amplitude. Thus, power is wasted during times when the system is transmitting at reduced amplitudes or not transmitting at all.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art.